While it has been long known to provide windows of the double-hung type which are also capable of tilting inwardly for convenient washing thereof, at least some of such constructions insofar as we are acquainted with them have usually involved the tilting and/or complete removal of portions of the window frame or they have suffered from a lack of acceptably tight sealing. Others of such tilt-type windows have involved excessively complex manipulations to effect the desired tilting and still others of them have not been readily conducive to manufacture from metallic sash and frame components. However, the speed of fabrication and resulting economy of windows made from metallic sash and frame components has long been recognized, together with the minimal maintenance characteristic of such windows, and hence it has long been desirable to provide a commercially acceptable window of the generally double-hung type, using metallic sash and frame components, capable of simple and easy tilting inward for cleaning but which will be sealed firmly against the entry of wind and water when in operating position.
Further, in order to adapt such a window to an extremely large market existing in older cities, or older parts of cities, wherein window openings especially for brick buildings already exist, exist in endless varieties of widths and heights, and are not readily modifiable, it is desirable to provide in addition a window construction which can be readily combined with other similar window units or combined with picture window or other related window units in a total window assembly for a single window opening and to do so quickly, reliably and without sacrifice in the speed and convenience by which same may be assembled or in the speed and versatility with which same may be associated with other similar or related units for fitting into building openings as required.